Specifically, drivers who test positive for marijuana or self-report using marijuana are more than twice as likely as other drivers to be involved in motor vehicle crashes.
Without having read the study, do you know if this statistic controls for age or anything else? If so, I stand corrected.
Thanks for your polite tone, it's not every day I get called a "fucking moron" before 7 a.m. :)
The study I linked to says: The data were stratified and analyzed according to study design, type of drug assessment, study time period, study location, or age of the study subjects. A more than 2-fold increased crash risk associated with marijuana use was found in each of the subsets of studies
Table 2 shows the age breakdown as "<25" and "all ages." See http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3276316/table/tb... .